Aqueous compositions and process for the surface modification of articles by use of the aqueous compositions

ABSTRACT

Use of an aqueous composition, which has been prepared by dissolving (A) dihydroxypropylchitosan and (B) 1,2,3,4-butanetetracarboxylic acid (B) in an aqueous medium, makes it possible to provide articles excellent in hydrophilicity, antibacterial and deodorant activities, touch feeling, antifogging property, paper strength, dyeability, waterproofness, antifouling property and/or the like.

TECHNICAL FIELD

This invention relates to aqueous compositions and also to a process forthe surface modification of articles by use of the aqueous compositions,and more specifically to aqueous compositions useful for modifyingsurfaces of articles and also to a process for the surface modificationof articles by use of the aqueous compositions. The present inventionprovides a variety of articles excellent in hydrophilicity,antibacterial and deodorant activities, touch feeling, antifoggingproperty, paper strength, dyeability, antifouling property and/or thelike.

BACKGROUND ART

An air conditioner provided with functions such as cooling, heating anddehumidification is equipped with heat-exchanging fins at its heatexchanger unit. In general, fin blanks for forming these heat-exchangingfins are made of aluminum or aluminum alloy as they are desired to havea light weight, excellent workability and superb thermal conductivity.

When such an air conditioner is operated in cooling mode, the heatexchanger unit is brought on an indoor side thereof to a temperatureequal to or lower than the dew point of moisture in the air so that themoisture in the air is caused to condense and adhere on the indoor finsarranged on the heat exchanger unit. The shape which the condensed watertakes on fin surfaces is determined depending on the wettability of thefin surfaces with water. On low-wettability fin surfaces, condensedwater tends to take the form of substantially hemispherical waterdroplets and further, to form water bridges between the fins, therebydeveloping resistance to a flow of air through the heat exchanger unitand hence, impairing the air flowability and further producing a noise.In some instances, condensed water may scatter around to soil theperipheries of the air conditioner.

With a view to overcoming these problems, it has already been practicedto subject fin blanks to hydrophilization treatment on their surfaces.Proposed methods include, for example, use of an inorganic hydrophilizercomposed of water glass or the like as a principal component (JP2-423895 B, JP 3-77440 B); and use of an organic hydrophilizer, such ascombined use of polyvinyl alcohol, a specific water-soluble polymer anda crosslinking agent (JP 1-299877 A), use of a polyacrylamide (JP1-270977 A), use of a copolymer of a particular hydrophilic vinylmonomer (JP 6-306247 A), and use of carboxymethylcellulose polymer,N-methylolacrylamide, polyacrylic acid or a zirconium compound (JapanesePatent No. 2,520,308).

The methods making use of inorganic hydrophilizers can impart excellenthydrophilicity to the surfaces of fin blanks. Nonetheless, they areaccompanied by a problem in that dies undergo severe wear upon pressingsuch fin blanks, because hydrophilic coatings formed on the surfaces ofthe fin blanks are made of a hard material composed of silica (SiO₂) asa principal component. They also involve another problem in that anunpleasant odor is felt in the beginning of cooling, as the hydrophiliccoatings have property of readily adsorbing unpleasant odor componentsfrom the surrounding environment.

In the methods making use of organic hydrophilizers, on the other hand,the hydrophilizers themselves serve as nutrient sources formicroorganisms so that microorganisms tend to grow in treatment bathsand on hydrophilic coatings. Prevention of their grow this, therefore,needed. In these methods, rot-proof property is hence imparted totreatment baths as needed. Addition of an antibacterial agent totreatment baths is more or less effective for the prevention of rottingof the treatment baths. Any attempt to impart antibacterial activity tocoatings themselves requires addition of the antibacterial agent in agreater amount, leading to a problem that the hydrophilicity of thecoatings is impaired. To allow the antibacterial activity of hydrophiliccoatings themselves to last longer, it has also been proposed to have anantibacterial substance dissolved out from the surfaces of thehydrophilic coatings. The hydrophilic coatings show antibacterialactivity as long as the antibacterial substance dissolves out, but thereis a limit to the period during which the antibacterial activity isexhibited.

With a view to imparting antibacterial activity to hydrophilic coatingsin an attempt to resolve the above-described problems, it has beenproposed to use, as a coating-forming material, chitosan havingantibacterial activity and to form a chitosan-containing coating on asurface of a fin blank (JP 7-190676 A). This method requires use of anorganic acid or an inorganic acid to form chitosan into an aqueoussolution, as chitosan is insoluble in water. However, this acid iswashed off with the above-described condensed water, resulting in aproblem that the chitosan coatings are deprived of film strength andantibacterial activity. Use of a polymer acid such as polyacrylic acidas the above-mentioned organic acid has also been proposed (JP 11-293149A). However, these methods which make use of chitosan are allaccompanied by a problem that a very unpleasant odor is given off uponand after baking a coating on a surface of a fin blank. Such fin blanksare, therefore, not satisfactory as fin blanks for use in airconditioners.

Most of the above-described conventional methods develop a problem that,unless anti-corrosion coating treatment such as chromate treatment isapplied to the surface of a fin blank before the formation of ahydrophilic coating thereon, the hydrophilic coating corrodes aluminumand powdering occurs when used for a long time. Upon surface treatmentof a fin blank, anti-corrosion undercoating treatment is hence required.The surface treatment, therefore, has to be conducted in two stages.This is not preferred economically.

Therefore, an object of the present invention is to provide an aqueouscomposition, which has the following features: an excellent hydrophiliccoating, which does not form water droplets, can be formed by applyingsingle-stage treatment, specifically by directly coating the aqueouscomposition onto an article and drying and curing the thus-coatedaqueous composition; the coating has excellent mechanical strength evenin a state wet with water (hereinafter the property is referred to aword “waterproof” or “waterproofness”), so that it is excellent inwaterproofness and corrosion resistance and also superb in lubricity,can withstand severe forming, and can exhibit sustainable hydrophilicitywithout being stained with adhered lube oil or the like; and moreover,the coating does not produce an unpleasant odor from the coating-formingmaterial and remains free from occurrence of microorganisms such as moldover a long period. In other word, the coating combines both excellentwaterproof strength and hydrophilicity. Another object of the presentinvention is to provide a process for the surface modification of anarticle by use of the aqueous composition.

DISCLOSURE OF THE INVENTION

The above-described objects can be achieve by the present invention tobe described hereinafter. Described specifically, the present inventionprovides an aqueous composition comprising, in a form dissolved in anaqueous medium, the following components (A) and (B):

-   -   (A) dihydroxypropylchitosan, and    -   (B) 1,2,3,4-butanetetracarboxylic acid [hereinafter referred to        as “BTC (B)”],        wherein the aqueous composition can form a waterproof coating        when dried and cured; and also, a process for modifying a        surface of an article, which comprises the following steps:        coating the aqueous composition onto the surface of the article;        and drying and curing the thus-coated aqueous composition.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will hereinafter be described in more detail basedon certain preferred embodiments.

“Dihydroxypropylchitosan (A)” required for the practice of the presentinvention is a substance disclosed in JP 59-8701 A, and can be obtained,for example, by reacting glycidol (2,3-epoxy-1-propanol) with chitosan,which is composed of 60 to 100% deacetylated chitin, at an appropriateratio. It is also available under a different name “glyceryl-chitosan”on the market for use in the present invention.

It is not absolutely necessary for dihydroxypropyl-chitosan (A) to be ina pure form. It may contain to some extent byproducts formed by theabove-described invention and unreacted substances, and may be in theform of powder or an aqueous solution. Dihydroxypropylchitosan includesthree chitosan derivatives, that is, N-(2,3-dihydroxypropyl)chitosan,O-(2,3-dihydroxypropyl)chitosan and N,O-(2,3-dihydroxypropyl)chitosan.These chitosan derivatives are all usable in the present invention. Itis, however, preferred to use N-(2,3-dihydroxypropyl)chitosan orN,O-(2,3-dihydroxypropyl)-chitosan or a mixture thereof.

The degree of dihydroxypropylation of dihydroxy-propylchitosan (A) foruse in the present invention may be preferably in a range of from about0.1 to 5, more preferably in a range of from 0.4 to 5. Its weightaverage molecular weight may preferably be 10,000 to 3,000,000, with arange of from 50,000 to 1,000,000 being more preferred. A weight averagemolecular weight lower than 10,000 results in the formation of a coatingof insufficient strength, while a weight average molecular weight higherthan 3,000,000 leads to an aqueous composition of excessively highviscosity so that there is no choice other than limiting theconcentration of dihydroxy-propylchitosan (A) to a considerably lowlevel.

On the other hand, BTC (B) required for the practice of the presentinvention is also a known substance by itself, and is available on themarket for use in the present invention. Incidentally, it is known touse BTC (B) in combination with a salt of a phosphorus oxo-acid as acatalyst for hydroxyl-containing, water-soluble polymers (JP 7-102110A). It was, on the other hand, not known that a coating ofwaterproofness was made by the reaction of dihydroxypropylchitosan (A)and BTC (B) alone without aid of catalyst such as a salt of a phosphorusoxo-acid. It should be emphasized that the reaction does not need theaddition of catalyst. Even if the reaction uses no catalyst, it leadsthe formation of strong waterproof and hydrophilic coating free fromgrowth of microorganisms such as mold. Furthermore, an unpleasant odorgenerates from the coating made by a reaction of dihydroxypropylchitosan(A) and crosslinking agents except BTC (B) and limits use of the systemstrictly. It was, however, not known that the reaction ofdihydroxypropylchitosan (A) and BTC (B) prevents the generation of theunpleasant odor.

The aqueous composition according to the present invention can beobtained by dissolving dihydroxypropyl-chitosan (A) and BTC (B) asessential components in an aqueous medium. Upon dissolution of theessential components in the aqueous medium, heating may be effected ifnecessary. The aqueous medium for use in the present invention maypreferably be distilled water, but depending on the application of theaqueous composition of the present invention, ordinary tap water may beused. As a further alternative, a mixed solvent of a hydrophilic organicsolvent such as an alcohol or a ketone and water may be used as needed.

Concerning the ratio of BTC (B) to Dihydroxypropyl-chitosan (A) to beused in the present invention, their weight ratio B/A in terms of solidsmay range from 0.1 to 3, preferably from 0.2 to 2. Use of BTC (B) at aB/A ratio smaller than 0.1 leads to the formation of a coating withinsufficient waterproofness, thereby failing to exhibit sufficientinhibitory effect on the production of an unpleasant odor fromdihydroxypropylchitosan during baking. On the other hand, use of BTC (B)at a B/A ratio greater than 3 results in the formation of a coating withlowered hydrophilicity and flexibility and also, is uneconomical becausethe water proofness of a coating is not improved in proportion with theamount of BTC.

As described above, the aqueous composition according to the presentinvention can be obtained by adding the above-described essentialcomponents in the aqueous medium and dissolving them optionally underheat. No particular limitation is imposed on the concentrations of theessential components. From the standpoint of workability upon using theaqueous composition, however, it is preferred that the total solidconcentration of the essential components falls within a range of from 1to 40 wt. %.

The aqueous composition according to the present invention may alsocontain a nonionic organic compound (C) or an organic compoundcontaining oxyalkylene units (ring-opened units of an alkylene oxide)(C′) in addition to dihydroxy-propylchitosan (A) and BTC (B).

Examples of the nonionic organic compound (C) and the organic compound(C′) containing oxyalkylene units can include, but are not limited to,polyethylene oxide, polypropylene oxide, polytetramethylene oxide,random or block copolymer of ethylene oxide and propylene oxide,polyvinyl alcohol, polyoxyethylene alkyl ethers, polyester containingoxyalkylene units, polyamide containing oxyalkylene units, graftcopolymer of polyvinyl alcohol with oxyethylene units, higher alkylethers, oxyethylene alkyl ethers, alkyl glycosides, alkylpolyglycosides, sucrose fatty acid esters, glycerin alkyl ethers, andglycerin alkyl esters. They can be used either singly or in combination.Concerning their molecular weights, no particular limitation is imposed.

If the article available from the use of the aqueous composition of thisinvention is subjected to severe forming such as deep drawing orspinning or ironing, it is very advantageous to have the nonionicorganic compound (C) or the organic compound containing oxyalkyleneunits (C′) included in the aqueous composition.

In this case, the ratio of the nonionic organic compound (C) or theorganic compound containing oxyalkylene units (C′) todihydroxypropylchitosan (A), C/A or C′/A may preferably range from 0.03to 3 in terms of solid weight ratio. A ratio smaller than 0.03 leads toa failure in exhibiting lubricity improving effect. A ratio greater than3 leads to saturation of the effect and is not preferred.

The aqueous composition according to the present invention may alsocontain a surfactant (D). As the surfactant (D), an anionic surfactant,a cationic surfactant or an amphoteric surfactant can be used. Examplescan include, but are not limited to, polyoxyethylene dodecyl amine,polyoxyethylene octadecyl amine, dimethyl dodecyl betaine, alkyl diaminoethyl glycines, N(N′-lanolin fatty acid amidepropyl)N-ethyl-N,N-dimethyl ammonium ethylsulfate, lauryl betaines,alkyl phosphate betaines, alkyl imidazolines, higher alcohol sulfateesters, higher alkyl ether sulfate esters, and dialkyl sulfosuccinatesalts.

The ratio of the surfactant (D) to dihydroxypropyl chitosan (A), D/A maypreferably range from 0.01 to 0.15 in terms of solid weight ratio. Theinclusion of the surfactant (D) in the aqueous composition can reduce adeterioration in hydrophilicity, which is caused by an auxiliarylubricant (coolant) coated on a surface of an article when the coatedarticle is subjected to forming. A solid weight ratio smaller than 0.01does not allow the resultant aqueous composition to exhibithydrophilicity improving effect. On the other hand, a solid weight ratiogreater than 0.15 results in a weak coating so that the waterproofnessand corrosion resistance of the coating deteriorate when the coating isleft over for a long time in a state wet with water. Solid weight ratiosoutside the above-described range are, therefore, not preferred.

To the aqueous composition according to the present invention, one ormore of other readily water-soluble chitosan and derivatives such ashydroxyethyl chitosan and hydroxy-propylchitosan, lower mono- ordi-carboxylic acids as auxiliary dissolvers, dihydrazides such as adipicacid dihydrazide as stabilizers, preservatives, mildewproofing agents,organic solvents, fine particulate fillers, lubricants, colorants andthe like. In particular, illustrative of the colorants (D′) are, fromthe standpoint of various durability, organic pigments such asphthalocyanin, azo, anthraquinone and quinacridone pigments; inorganicpigments such as titanium oxide, iron oxide and composite metal oxides;and carbon black. In the composition according to the present invention,these colorants (D′) may be used in a range accounting for 0.1 to 10 wt.%.

The aqueous composition of the present invention obtained as describedabove, despite its inclusion of BTC (B), remains stable withoutthickening or gelling even when left over at 5 to 30° C. for 1 month orlonger. Accordingly, it can be used as a one-pack treatment. By coatingthe aqueous composition on a surface of an article and drying and curingthe thus-coated aqueous composition, a hydrophilic coating excellent inwaterproofness is formed. As the coating under formation is exposed toan ultimate temperature of 100° C. or higher during the drying orcuring, the coating is obtained as a waterproof coating firmed adheredon the surface of the article.

The aqueous composition according to the present invention is useful invarious applications. For example, particles of dihydroxypropylchitosan,said particles having high hydrophilicity, can be obtained by spraydrying the aqueous composition. These particles are useful, for example,as a support for various chromatographic techniques. The aqueouscomposition of the present invention is also useful as a surfacemodifier for various fiber products made of natural or synthetic fibers,paper, synthetic fiber, wood, glass, ceramics, pottery and chinaware,and synthetic resin articles, and provides a variety of productsexcellent in hydrophilicity, antibacterial and deodorant activities,touch feeling, antifogging property, paper strength, dyeability,waterproofness, antifouling property and/or the like. The aqueouscomposition according to the present invention is also useful as asurface treatment for metal articles especially made of at least onemetal selected from the group consisting of iron, copper, aluminum andalloys thereof. A description will hereinafter be made taking as arepresentative example an application of the aqueous composition of thepresent invention to an aluminum-made fin blank for an air conditioner.

No particular limitation is imposed on a process for forming ahydrophilic coating on a surface of the aluminum-made fin blank. Thisprocess, however, can be conducted, for example, as will hereinafter bedescribed by taking a heat-exchanging fin blank as an example.

Firstly, degreasing is applied to the surface of the aluminum blank.Illustrative examples of usable degreasing media can include, but arenot specifically limited to, solvents, surfactants, aqueous alkalinesolutions, and aqueous acidic solutions. If the surface is not smearedor covered with oil or dust, degreasing may be conducted by simplywashing the surface with warm water of 60 to 80° C. For permittingdirect coating of the aqueous composition of the present invention, itis important to obtain a clean aluminum surface.

The aqueous composition according to the present invention is directlycoated on an aluminum surface and is then dried and cured. For theprovision of further improved corrosion resistance, it is more preferredto apply certain anti-corrosion coating treatment to the aluminumsurface in advance. No particular limitation is imposed on the treatmentmethod and the type of a corrosion-resistant coating to be obtained.Illustrative of the treatment method are dipping treatment, sprayingtreatment and coating treatment. Examples of the corrosion-resistantcoating can include inorganic corrosion-resistant coatings such asphosphorus chromate and zirconium coatings; and organiccorrosion-resistant coatings such as urethane resin, acrylic resin andphenol resin coatings.

Onto the cleaned surface of the aluminum fin blank, the aqueouscomposition according to the present invention is coated by a suitablecoating method, for example, roll coating, bar coating, spray coating ordip coating to give a dry coat weight of from 0.01 to 10 g/m². Thethus-coated aqueous composition is then dried and cured under conditionsconsisting of an ultimate temperature of at least 100° C., morepreferably from 130 to 220° C. and a curing time of from 1 second to 30minutes such that a hydrophilic coating is formed on the surface of thefin blank. The heat-exchanging fin blank obtained as described above iscoated with an auxiliary lube oil, subjected to forming and then dried,so that fins for a heat exchanger are obtained as intended.

The aqueous composition according to the present invention may also beapplied to a heat exchanger assembled of aluminum components(post-coating treatment). In this case, no auxiliary lube oil is neededso that the heat exchanger is free of its effects.

When the heat-exchanging fins formed as described above are used asindoor fins in a cooling apparatus, water condensed by cooling spreadsover the surfaces of the fins so that no water droplets are formed. Asthe condensed water does not form droplets, no bridges are formedbetween the fins. Further, the condensed water neither causes a noisenor scatters around to soil the peripheries. Moreover, the coatingformed from the aqueous composition according to the present inventiondoes not give off an odor even during its baking, although it is anorganic coating. In addition, the coating has substantial antibacterialand deodorant activities. Even when the fins equipped with the coatingare assembled in an air conditioner such as a room cooling apparatus ora car cooler and are repeatedly used over a long time, no unpleasantodor based on the coating forming material, no musty odor or no otherunpleasant odor is given off during its use, to say nothing of theinitial stage of its use. Moreover, no powdering takes place during useover a long time even when anti-corrosion coating treatment led bychromate treatment is not applied.

EXAMPLES

The present invention will next be described more specifically based onExamples and Comparative Examples, in which all designations of “%” areon a weight basis. It should however be borne in mind that the presentinvention is not limited by these Examples. The formulas of aqueouscompositions employed as examples and comparative examples are presentedin Table 1-1 to Table 1-3.

Preparation procedures of the aqueous compositions employed as exampleswill hereinafter be described.

Example 1

Dihydroxypropylchitosan (degree of dihydroxypropyla-tion: 1.1, MW:100,000) (5 g) was dispersed in purified water (80 g). Subsequent toaddition of BTC (15 g), the resulting mixture was stirred fordissolution at room temperature for 4 hours to prepare an aqueouscomposition according to the present invention.

Examples 2-19

Aqueous compositions according to the present invention were prepared ina similar manner as in Example 1 except that the degree ofdihydroxypropylation and weight average molecular weight (MW) ofdihydroxypropylchitosan and the mixing ratio of BTC todihydroxypropylchitosan were changed as shown in Table 1-1 and Table1-2.

Example 20

Dihydroxypropylchitosan (degree of dihydroxypropyla-tion: 1.1, MW:100,000) (5 g) was dispersed in purified water (70 g). Subsequent toaddition of BTC (5 g), the resulting mixture was stirred for dissolutionat room temperature for 4 hours. An aqueous solution (5 g) ofpolyethylene oxide (MW: 20,000), the concentration of which had beenadjusted to 5%, was added, followed by the addition of purified water togive a total amount of 100 g. The thus-prepared mixture was stirred for30 minutes to obtain an aqueous composition according to the presentinvention.

Example 21

Dihydroxypropylchitosan (degree of dihydroxypropyla-tion: 1.1, MW:100,000) (5 g) was dispersed in purified water (50 g). Subsequent toaddition of BTC (5 g), the resulting mixture was stirred for dissolutionat room temperature for 4 hours. An aqueous solution (12.5 g) of PEO(product of Sanyo Chemical Industries, Ltd., MW: 20,000), theconcentration of which had been adjusted to 40%, and an aqueous solution(12.5 g) of a PEO-PPO copolymer (a copolymer of polyethylene oxide andpolypropylene oxide), the concentration of which had been adjusted to40%, were then added. Finally, purified water was added to give a totalamount of 100 g, whereby an aqueous composition according to the presentinvention was obtained.

Example 22

An aqueous composition according to the present invention was obtainedin a similar manner as in Example 20 except that, before the totalamount was finally adjusted with purified water, an aqueous solution (5g) of sodium polyoxyethylene lauryl ether sulfate (the number of molesof added ethylene: 2), the concentration of which had been adjusted to10%, was added.

Example 23

An aqueous composition according to the present invention was obtainedin a similar manner as in Example 20 except that, before the totalamount was finally adjusted with purified water, an aqueous solution (10g) of 2-methylcarboxymethylhydroxy-ethyl imidazolinium, theconcentration of which had been adjusted to 10%, was added.

Example 24

A colored aqueous composition according to the present invention wasprepared in a similar manner as in Example 20 except that the 5% aqueoussolution (5 g) of polyethylene oxide was replaced by a 5% aqueoussolution (4 g) of polyvinyl alcohol (“DENKA POVAL K05”, trade name;product of Denki Kagaku Kogyo Kabushiki Kaisha)and an aqueous dispersion(1 g) of phthalocyanine blue pigment, said aqueous dispersion having asolid content of 40%.

Example 25

An aqueous composition according to the present invention was obtainedin a similar manner as in Example 21 except that, before the totalamount was finally adjusted with purified water, an aqueous solution (10g) of 2-methylcarboxymethylhydroxy-ethyl imidazolinium, theconcentration of which had been adjusted to 10%, was added.

Preparation procedures of the aqueous compositions employed ascomparative examples will hereinafter be described.

Comparative Example 1

Comparative Example 1 was an aqueous composition making use of lacticacid as an acid component. Dihydroxypropyl-chitosan (degree ofdihydroxypropylation: 1.1, MW: 100,000) (5 g) was dispersed in purifiedwater (80 g). Subsequent to addition of lactic acid (5 g), the resultingmixture was stirred for dissolution at room temperature for 4 hours.Purified water was then added to give a total amount of 100 g, wherebyan aqueous composition of this comparative example was obtained.

Comparative Example 2

Comparative Example 2 was an aqueous composition making use of lacticacid as an acid component and used lactic acid at a smaller ratiorelative to dihydroxypropylchitosan than Comparative Example 1.Dihydroxypropylchitosan (degree of dihydroxypropylation: 2.2, MW:70,000) (10 g) was dispersed in purified water (80 g). Subsequent toaddition of lactic acid (5 g), the resulting mixture was stirred fordissolution at room temperature for 4 hours. Purified water was thenadded to give a total amount of 100 g, whereby an aqueous composition ofthis comparative example was obtained.

Comparative Example 3

Comparative Example 3 was an aqueous composition making use of chitosannot subjected to dihydroxypropylation (degree of dihydroxypropylation:0; MW: 100,000; hereafter simply called “chitosan”). The aqueouscomposition of this comparative example was obtained in a similar manneras in Example 1.

Comparative Example 4

Chitosan (3 g) was dispersed in purified water (50 g) Subsequent toaddition of citric acid(6g), the resulting mixture was stirred at roomtemperature for 4 hours. Thereafter, a 20% aqueous solution (35 g) ofpolyacrylic acid (“Jurymer AC10H”, trade name; MW: 50,000; product ofNihon Junyaku Co., Ltd.) was added. Purified water was then added togive a total amount of 100 g, whereby an aqueous composition of thiscomparative example was obtained.

Comparative Example 5

An aqueous solution (50 g) of polyvinyl alcohol (“DENKA POVAL K05”,trade name; product of Denki Kagaku Kogyo Kabushiki Kaisha), theconcentration of which had been adjusted to 10%, was added to purifiedwater (30 g). Subsequent to addition of BTC (5 g), the resulting mixturewas stirred at room temperature for 1 hour. Purified water was finallyadded to give a total amount of 100 g, whereby an aqueous composition ofthis comparative example was obtained.

Comparative Example 6

An aqueous solution (50 g) of polyvinyl alcohol (“DENKA POVAL K05”,trade name; product of Denki Kagaku Kogyo Kabushiki Kaisha), theconcentration of which had been adjusted to 10%, was added to purifiedwater (30 g). Subsequent to addition of a 65% aqueous solution (4 g) ofa urea resin (“Cymel UFR65”, trade name; product of Mitsui Chemicals,Inc.), the resulting mixture was stirred for 1 hour. Further, a solution(10 g) of a polyamide resin (“AQ Nylon P-70”, trade name; product ofToray Industries, Inc.), the concentration of which had been adjusted to50%, was added, followed by stirring at room temperature for 1 hour.Purified water was finally added to give a total amount of 100 g,whereby an aqueous composition of this comparative example was obtained.

TABLE 1-1 Aqueous Compositions Component(s) Component(s) Component (A)Component (B) (C) and/or C′ (D) and/or D′ Water Degree of Parts PartsParts Parts Parts dihydroxy- MW by by by by by propylation (× 10⁴)weight Kind weight Kind weight Kind weight weight Ex. 1 1.1 10 5 BTC 15— — — — 80 Ex. 2 1.1 10 5 BTC 10 — — — — 85 Ex. 3 1.1 10 5 BTC 5 — — — —90 Ex. 4 1.1 10 5 BTC 1 — — — — 94 Ex. 5 0.5 9 5 BTC 5 — — — — 90 Ex. 61.8 10 5 BTC 5 — — — — 90 Ex. 7 3.7 11 5 BTC 5 — — — — 90 Ex. 8 5 13 5BTC 5 — — — — 90 Ex. 9 1.1 5 15 BTC 15 — — — — 70 Ex. 10 1.1 40 3 BTC 3— — — — 94 Ex. 11 2.2 7 10 BTC 5 — — — — 85 Ex. 12 2.3 70 1.5 BTC 1 — —— — 97.5

TABLE 1-2 Aqueous Compositions Component(s) Component(s) Component (A)Component (B) (C) and/or C′ (D) and/or D′ Water Degree of Parts PartsParts Parts Parts dihydroxy- MW by by by by by propylation (× 10⁴)weight Kind weight Kind weight Kind weight weight Ex. 13 1.1 10 5 BTC1.5 — — — — 93.5 Ex. 14 1.3 8 5 BTC 5 — — — — 90 Ex. 15 1.3 8 5 BTC 5 —— — — 90 Ex. 16 1.3 8 5 BTC 5 — — — — 90 Ex. 17 1.1 10 5 BTC 0.3 — — — —94.7 Ex. 18 0.25 9 5 BTC 5 — — — — 90 Ex. 19 1.3 8 5 BTC 5 — — — — 90Ex. 20 1.1 10 5 BTC 5 PEO 0.25 — — 89.75 Ex. 21 1.1 10 5 BTC 5 PEO/ 5/5— — 80 PEO + PPO Ex. 22 1.1 10 5 BTC 5 PEO 0.25 Anionic 0.5 89.25surfactant Ex. 23 1.1 10 5 BTC 5 PEO 0.25 Amphoteric 1 88.75 surfactantEx. 24 1.1 10 5 BTC 5 PVA 0.20 Colorant 0.4 89.4

TABLE 1-3 Aqueous Compositions Component(s) Component(s) Component (A)Component (B) (C) and/or C′ (D) and/or D′ Water Degree of Parts PartsParts Parts Parts dihydroxy- MW by by by by by propylation (× 10⁴)weight Kind weight Kind weight Kind weight weight Ex. 25 1.1 10 5 BTC 5PEO/ 5/5 Amphoteric 1 79 PEO + PPO surfactant Comp. 1.1 10 5 Lactic 5 —— — — 90 Ex. 1 acid Comp. 2.2 7 10 Lactic 5 — — — — 85 Ex. 2 acid Comp.Chitosan (5 parts), BTC (15 parts) 80 Ex. 3 Comp. Chitosan (3 parts),polyacrylic acid (7 parts), citric acid (6 parts) 84 Ex. 4 Comp. PVA (5parts), BTC (5 parts) 90 Ex. 5 Comp. PVA (5 parts), urea resin (2.6parts), polyamide resin (5 parts) 87.4 Ex. 6 Component (A):Dihydroxypropylchitosan, component (B): BTC, component (C): nonionicorganic compound, component (C′): organic compound containingoxyalkylene units, component (D): surfactant, component (D′): colorant,PVA: polyvinyl alcohol. Parenthesized parts in Comparative Examples 3-6mean “parts by weight”. Polyacrylic acid: “Jurymer AC10H” (trade name,product of Nihon Junyaku Co., Ltd.; solid concentration: 20%; MW:50,000) was used. Polyvinyl alcohol: “DENKA POVAL K05” (trade name,product of Denki Kagaku Kogyo Kabushiki Kaisha) was used. Urea resin:“Cymel UFR65” (trade name, product of Mitsui Chemicals, Inc.; solidconcentration: 65%) was used. Polyamide resin: “AQ Nylon P-70” (tradename, product of Toray Industries, Inc.; 100%) was used.

Using the aqueous compositions prepared in accordance with the formulasshown in Table 1-1 to Table 1-3, aluminum blanks with hydrophiliccoatings were obtained by the below-described hydrophilic coatingforming procedure, and by the below-described ranking methods, theirranking tests were conducted. The results of the ranking are presentedin Table 2-1 to Table 2-5.

Procedure of Pretreatment

An alkaline degreasing agent, “Fine Cleaner 4377K” (trade name; productof Nihon Parkerizing Co., Ltd.) was diluted to 2% concentration with tapwater to provide an aqueous solution. Against a surface of each aluminumsheet (JIS 1050) of 100 to 110 μm in thickness, the aqueous solution wassprayed at 60° C. for 10 seconds to conduct alkaline degreasing. Thealuminum sheet was then washed with tap water and dried to provide aclean aluminum surface.

Forming Procedure of Hydrophilic Coating

Onto surfaces of aluminum sheets (10 cm×10 cm) cleaned by alkalinedegreasing treatment as described above, the aqueous compositions ofExamples 1-25 and Comparative Examples 1-6 were coated by a bar coaterto give dry coat weights of 1 g/m², respectively. The aluminum sheetswith the aqueous compositions coated thereon were then dried and curedunder the corresponding conditions shown in Table 2-1 to Table 2-5 toprovide as specimens for use in the following ranking tests.

(1) Odorlessness Ranking Test

Using those specimens, an organoleptic test was conducted immediately.Their smells were ranked in 6 stages in accordance with the followingranking standard.

Ranking Standard

-   -   5: Does not smell even when a specimen is smelled after        breathing upon it.    -   4: Very slightly smells when a specimen is smelled after        breathing upon it.    -   3: Does not smell when no breath is blown upon a specimen, but        slightly smells when the specimen is smelled after breathing        upon it.    -   2: Does not smell when no breath is blown upon a specimen, but        smells when the specimen is smelled after breathing upon it.    -   1: Noticeably smells even when no breath is blown upon a        specimen.    -   0: Strongly smells even when no breath is blown upon a specimen.        (2) Waterproofness Ranking Test

Each specimen was immersed in purified water for 24 hours, and was thendried for 30 minutes in a blast dryer controlled at 100° C. After thespecimen was allowed to cool down to room temperature, the specimen wasweighed. A coat remainder percent was determined in accordance with thebelow-described equation, and the waterproofness of the specimen wasranked in 5 stages in accordance with the following ranking standard.${{Coat}\quad{remainder}\quad{percent}} = {\frac{C - A}{B - A} \times 100\quad(\%)}$wherein

-   -   A: Weight of an aluminum sheet before hydrophilizing surface        treatment.    -   B: Weight of the aluminum sheet after the hydrophilizing surface        treatment.    -   C: Weight of the aluminum sheet after dipped for 24 hours in        water subsequent to the hydrophilizing surface treatment.        Ranking Standard for Waterproofness    -   5: Percent coat remainder≧95%    -   4: 95%>coat remainder percent≧80%    -   3: 80%>coat remainder percent≧70%    -   2: 70%>coat remainder percent≧50%    -   1: 50%>coat remainder percent        (3) Hydrophilicity Ranking Test        (3)-1 Initial Hydrophilicity

Purified water (2 μL) was dropped onto the surface of each specimen heldin a horizontal position. The contact angle of a water droplet so formedwas measured by a contact angle meter (“CA-X Model”, trade name;manufactured by KYOWA INTERFACE SCIENCE CO., LTD.) to rank its initialhydrophilicity in accordance with the following ranking standard.

Ranking Standard for Initial Hydrophilicity

-   -   5: Contact angle<5°    -   4: 5°≦contact angle<10°    -   3: 10°≦contact angle<15°    -   2: 15°≦contact angle<20°    -   1: 20°≦contact angle<30°    -   0: 30°≦contact angle        (3)-2 Sustainable Hydrophilicity

After each specimen was dipped for 1 minute in a volatile pressing oil,“RF-190” (trade name, product of Show a Shell Sekiyu K.K.), the specimenwas dried at 150° C. for 5 minutes. Two types of specimens, one nottreated with the volatile pressing oil (sustainable hydrophilicity A)and the other treated with the volatile pressing oil (sustainablehydrophilicity B), were immersed for 200 hours in flowing purified waterand were then dried for 1 hour in a blast dryer controlled at 80° C.After drying, the contact angles of water droplets were measured in asimilar manner as in the initial hydrophilicity test to rank theirsustainable hydrophilicity in accordance with the following rankingstandard.

Ranking Standard for Sustainable Hydrophilicity A

-   -   5: Contact angle<10°    -   4: 10°≦contact angle<15°    -   3: 15°≦contact angle<20°    -   2: 20°≦contact angle<30°    -   1: 30°≦contact angle<40°    -   0: 40°≦contact angle        Ranking Standard for Sustainable Hydrophilicity B    -   5: Contact angle<10°    -   4: 10°≦contact angle<20°    -   3: 20°≦contact angle<30°    -   2: 30°≦contact angle<40°    -   1: 40°≦contact angle<50°    -   0: 50°≦contact angle        (4) Corrosion Resistance Ranking Test

Each specimen was subjected to a salt spray test up to the 500^(th)hour. After purified water was caused to run on and along the surface ofthe specimen, the specimen was dried for 1 hour in a blast dryercontrolled at 100° C., and its external appearance was ranked inaccordance with the following ranking standard.

Ranking Standard for Corrosion Resistance

-   -   5: Corrosion area percent=0%    -   4: 0%<corrosion area percent<5%    -   3: 5%≦corrosion area percent<10%    -   2: 10%≦corrosion area percent<30%    -   1: 30%≦corrosion area percent<70%    -   0: 70%≦corrosion area percent        (5) Lubricity Ranking Test

To investigate the lubricity of the surface of each specimen, its Bowdencoefficient of friction was measured. On the surface of the specimen seton a stage of a Bowden ball/plane friction and wear tester (manufacturedby Toyo Baldwin Co.), a {fraction (1/16)}″ steel ball was caused toslide to calculate an initial coefficient of friction. The followingranking standard was followed.

Ranking Standard for Lubricity

-   -   5: Coefficient of friction<0.1    -   4: 0.1≦coefficient of friction<0.15    -   3: 0.15≦coefficient of friction<0.2    -   2: 0.2≦coefficient of friction<0.3    -   1: 0.3≦coefficient of friction<0.4    -   0: 0.4≦coefficient of friction

The ranking of lubricity makes it possible to simulate formability. Ascore of at least 3 by the above-described ranking standard indicates aformability level which poses no problem in actual use.

TABLE 2-1 Results of Ranking Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 MetalAl Cu Al Al Al Al Pretreatment Degreasing Degreasing Degreasing Note 2Degreasing Degreasing only only only only only Drying and curingconditions Temp. (° C.) 200 200 200 200 200 200 Time 30 sec 30 sec 30sec 30 sec 30 sec 30 sec Ranked property Odorlessness 5 5 5 4 5 5Waterproofness 4 4 5 5 4 5 Initial 4 4 5 4 4 5 hydrophilicitySustainable 4 4 5 4 4 5 hydrophilicity A Sustainable 4 4 4 4 4 4hydrophilicity B Corrosion 5 Note 1 5 5 5 5 resistance Lublicity 4 4 4 44 4 Note 1: In Example 2, copper (JIS C1220) was used as a metal and theranking of corrosion resistance was omitted. Note 2: In Example 4,phosphorus chromate treatment was applied as pretreatment. Spray-treatedat 50° C. for 5 seconds with “ALCHROM K702” (trade name, product ofNihon Parkerizing Co., Ltd.) to give a Cr coat weight of 20 mg/m².

TABLE 2-2 Results of Ranking Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12Metal Al Al Al Al Al Al Pretreatment Degreasing Degreasing DegreasingDegreasing Degreasing Degreasing only only only only only only Dryingand curing conditions Temp. (° C.) 200 200 200 200 200 200 Time 30 sec30 sec 30 sec 30 sec 30 sec 30 sec Ranked property Odorlessness 5 5 5 55 5 Waterproofness 5 5 5 5 5 5 Initial 5 5 5 5 5 5 hydrophilicitySustainable 5 5 5 5 5 5 hydrophilicity A Sustainable 4 4 4 4 4 4hydrophilicity B Corrosion 4 5 5 5 4 4 resistance Lublicity 4 4 4 4 4 4

TABLE 2-3 Results of Ranking Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18Metal Al Al Al Al Al Al Pretreatment Degreasing Degreasing DegreasingDegreasing Degreasing Degreasing only only only only only only Dryingand curing conditions Temp. (° C.) 220 220 160 130 200 200 Time 1 min 15sec 1 min 30 min 30 sec 30 sec Ranked property Odorlessness 4 5 4 5 3 5Waterproofness 4 5 4 5 3 4 Initial 4 5 4 4 4 3 hydrophilicitySustainable 4 5 5 5 3 3 hydrophilicity A Sustainable 4 4 4 4 3 3hydrophilicity B Corrosion 5 5 4 4 4 4 resistance Lublicity 4 4 4 4 4 4

TABLE 2-4 Results of Ranking Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24Ex. 25 Metal Al Al Al Al Al Al Al Pretreatment Degreasing DegreasingDegreasing Degreasing Degreasing Degreasing Degreasing only only onlyonly only only only Drying and curing conditions Temp. (° C.) 90 200 200200 200 200 200 Time 30 min 30 sec 30 sec 30 sec 30 sec 30 sec 30 secRanked property Odorlessness 3 5 5 5 5 5 5 Waterproofness 4 5 5 4 4 4 3Initial 4 5 5 5 5 5 5 hydrophilicity Sustainable 3 5 5 5 5 5 5hydrophilicity A Sustainable 4 4 4 5 5 5 5 hydrophilicity B Corrosion 35 5 4 4 4 3 resistance Lublicity 3 5 5 5 5 5 5

TABLE 2-5 Results of Ranking Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Metal Al Al Al Al Al Al PretreatmentDegreasing Degreasing Degreasing Degreasing Degreasing Degreasing onlyonly only only only only Drying and curing conditions Temp. (° C.) 200200 200 200 200 200 Time 30 sec 30 sec 30 sec 30 sec 30 sec 30 secRanked property Odorlessness 0 0 4 0 2 4 Waterproofness 2 2 4 1 4 4Initial 3 4 2 4 3 3 hydrophilicity Sustainable 1 1 2 1 2 2hydrophilicity A Sustainable 0 0 1 0 0 0 hydrophilicity B Corrosion 2 21 0 2 2 resistance Lublicity 1 1 2 2 1 2

Concerning the ranking results, scores of at least 3 are not consideredto pose any problem in actual use.

As is readily envisaged from the results of Table 2-1 to Table 2-5, goodresults were obtained in all of odorlessness, waterproofness andhydrophilicity owing to the use of BTC (B) in the present invention. InExamples 1-4, the aqueous compositions were prepared by adding BTC invaried amounts. The results of their ranking shown in Table 2-1 weregood. In Examples 5-8, the aqueous compositions were prepared by usingdihydroxypropylchitosan samples (A) of varied degrees ofdihydroxypropylation. The results of their ranking were good. InExamples 9-12, the tests were carried out using dihydroxypropylchitosansamples (A) of varied weight average molecular weights and the resultantaqueous compositions had different concentrations. In Examples 13-16,the tests were conducted with varied drying and curing conditions. Theresults of Examples 9-16 were all acceptable.

Further, good performance was achieved even when a hydrophilic coatingwas applied to a different metal as in Example 2 or even whenanti-corrosion coating treatment was applied as pretreatment as inExample 4.

In Example 17, the aqueous composition was prepared using BTC (B) anddihydroxypropylchitosan (A) at a B/A weight ratio of 0.06. Performancewas slightly lowered in odorlessness, waterproofness and sustainablehydrophilicity. In Example 18, the use of dihydroxypropylchitosan (A)the degree of dihydroxypropylation of which was 0.25 resulted insomewhat lowered hydrophilicity. From these results, it is appreciatedthat the more preferred weight ratio of BTC (B) todihydroxypropylchitosan (A), B/A, is in a range of from 0.1 to 3 andalso that the more preferred degree of dihydroxy-propylation ofdihydroxypropylchitosan (A) is in a range of from 0.4 to 5.

From Example 19, it is considered that a drying or curing temperaturelower than 100° C. leads to some reductions in sustainablehydrophilicity, corrosion resistance and lubricity and hence, that thedrying or curing temperature is preferably 100° C. or higher.

In Examples 20-25, the aqueous compositions of dihydroxypropylchitosan(A) and BTC (B) were added with a nonionic organic compound (C) or anorganic compound (C′) having oxyalkylene units, a surfactant (D) or acolorant (D′). Those aqueous compositions led to improvements in bothsustainable hydrophilicity and lubricity after treatment with thepressing oil than the aqueous compositions of Examples 1-19. It is,therefore, understood that the aqueous compositions of Examples 20-24are more preferred when articles with hydrophilic coatings appliedthereon are subjected to smearing with pressing oil and/or to severeforming.

From Example 25, it is considered that use of a surfactant (D) anddihydroxypropylchitosan (A) at a D/A weight ratio of 0.2 leads to somereductions in corrosion resistance and waterproofness and accordingly,that a D/A weight ratio of 0.15 or lower is more preferred.

Incidentally, none of the aqueous compositions employed in the Examplesdeveloped thickening or gelling even after an elapsed time of 30 days.

In Comparative Examples 1 and 2, the aqueous compositions were preparedby changing the acid component from BTC (B) to lactic acid. This changeled to deteriorations in odorlessness, waterproofness, sustainablehydrophilicity and lubricity.

In Comparative Example 3, the aqueous composition was prepared usingundihydroxypropylated, simple chitosan and BTC (B). The aqueouscomposition gave poor results in all properties except odorlessness andwaterproofness.

In Comparative Example 4, the aqueous composition was prepared usingchitosan and polyacrylic acid. The aqueous composition gave poor resultsin odorlessness, waterproofness, sustainable hydrophilicity andcorrosion resistance.

In Comparative Examples 5-6, the aqueous compositions were preparedusing other water-soluble high molecular compounds. Both of the aqueouscompositions gave poor results in the sustainable hydrophilicity aftertreated with the pressing oil.

A description will next be made about some other application examples ofaqueous composition according to the present invention.

Application Example 1

Dihydroxypropylchitosan (degree of dihydroxypropylation: 1.1, molecularweight: 100,000) and BTC were formulated at a weight ratio of 1:1 intoan aqueous solution having a dihydroxypropylchitosan concentration of0.5%. A cloth which was 40 by 40 centimeters square was dipped in theaqueous solution, and the aqueous solution was wrung out of the cloth ata wringing rate of 100% on a roll wringer. The cloth was subjected toheat treatment at 150° C. for 5 minutes in a hot-air dryer, and awaterproof coating was fixedly applied on the cloth. The touch feelingof the thus-treated cloth was soft. The antibacterial activity of thetreated cloth was determined in accordance with JIS L1902-98.

-   -   Sample bacteria: Staphylococcus aureus    -   Cyclic washing (10 cycles, JIS L0217 103)    -   Acceptability standard: bacteriostatic activity≧2.2

Bacteriostatic activity Before washing After washing Cotton 5.1 4.3Polyester/cotton mixed 4.5 3.9 Acrylic fibers 3.5 3.0 Silk 4.2 4.0 Wool3.7 3.0

From the above results, it was found that the cloths treated inaccordance with the present invention retained sufficient antibacterialactivity even after washed 10 times.

Application Example 2

A solution, which had been prepared by adding isopropyl alcohol to theaqueous composition of Example 1 at a weight ratio of 1:1, was coatedonto a transparent polyester film, a white paper sheet and a laminatedwood board by a bar coater to give dry coat weights of 0.5 g/m²,respectively, followed by heat treatment at 130° C. for 3 minutes in ahot-air dryer. A single droplet of water was dropped onto the treatedsurface of the treated polyester film, and the treated surface wasobserved for possible changes. No marked swelling was observed on thecoating and, even when rubbed, the coating was not separated. Using adye-based ink, the treated white paper sheet was printed by an ink-jetprinter manufactured by Seiko Epson Corporation. The treated white papersheet was successfully printed without any problem. For the sake ofcomparison, the printed, treated paper sheet and an untreated papersheet printed likewise were left over for 1 day, and water was droppedonto their printed surfaces. The prints blotted in the case of theuntreated paper sheet, while the prints remained substantially free fromblotting in the case of the paper sheet treated in accordance with thepresent invention. The treatment of the present invention was,therefore, effective for the setting of the dye. Further, a picture wasdrawn with a paint brush on the surface of the laminated wood boardtreated by the process of the present invention. Compared with anuntreated laminated wood board, the treated laminated wood board wasexcellent in the development of light colors and, after drying, providedthe picture with better waterproofness.

Application Example 3

The aqueous composition of Example 1 was coated onto the glass surfaceof a mirror to give a dry coat weight of 1 g/m², followed by heattreatment at 180° C. for 2 minutes. The thus-treated mirror was placedin a bathroom, and was observed for its fogging or clouding with steamand adhesion of water droplets. The mirror had good antifoggingproperty. Further, the treated mirror was immersed for 24 hours in waterand the pencil hardness of the treated surface was measured. Its pencilhardness was found to be “H”, and the adhesion of the coating was alsogood.

CAPABILITY OF EXPLOITATION IN INDUSTRY

As has been described above, the present invention can provide aqueouscompositions and also a process for the surface modification of articlesby use of the aqueous compositions. The aqueous compositions and surfacemodification process have characteristic features. Describedspecifically, each aqueous composition can form an excellent hydrophiliccoating, which does not permit formation of water droplets thereon, byapplying single-stage treatment, specifically by applying the aqueouscomposition directly onto a surface of an article and drying and curingthe same. Moreover, this coating has excellent waterproof strength evenin a state wet with water, and therefore, is excellent in waterproofnessand corrosion resistance. The coating has superb lubricity so that itcan withstand severe forming. The coating can exhibit sustainablehydrophilicity without being smeared with adhered lube oil or the like.In addition, the coating gives off no unpleasant odor from thecoating-forming material and remains free from occurrence ofmicroorganisms such as mold over a long time.

1. An aqueous composition comprising, in a form dissolved in an aqueousmedium, the following components (A) and (B): (A)dihydroxypropylchitosan, and (B) 1,2,3,4-butanetetracarboxylic acid,wherein said aqueous composition can form a waterproof coating whendried and cured.
 2. An aqueous composition according to claim 1, whereina weight ratio of 1,2,3,4-butanetetracarboxylic acid (B) todihydroxypropylchitosan (A), B/A is 0.1 to 3 in terms of solids.
 3. Anaqueous composition according to claim 1, whereindihydroxypropylchitosan (A) has a weight average molecular weight offrom 10,000 to 3,000,000.
 4. An aqueous composition according to claim1, wherein dihydroxypropylchitosan (A) has a degree ofdihydroxy-propylation of from 0.1 to
 5. 5. An aqueous compositionaccording to claim 1, wherein said aqueous composition has a solidconcentration of from 1 to 40 wt. %.
 6. An aqueous composition accordingto claim 1, further comprising the following component (C): (C) anonionic organic compound, a weight ratio of said nonionic organiccompound (C) to dihydroxypropylchitosan (A), C/A being 0.03 to 3 interms of solids.
 7. An aqueous composition according to claim 1, furthercomprising the following component (C′): (C′) an organic compoundcontaining oxyalkylene units, a weight ratio of said organic compound(C′) to dihydroxy-propylchitosan (A), C′/A being 0.03 to 3 in terms ofsolids.
 8. An aqueous composition according to claim 1, furthercomprising the following component (D): (D) a surfactant, a weight ratioof said surfactant (D) to dihydroxypropyl-chitosan (A), D/A being 0.01to 0.15 in terms of solids.
 9. An aqueous composition according to claim1, further comprising a colorant.
 10. A process for modifying a surfaceof an article, which comprises the following steps; coating an aqueouscomposition as defined in claim 1 onto said surface of said article; anddrying and curing the thus-coated aqueous composition.
 11. A surfacemodification process according to claim 10, wherein said aqueouscomposition is coated at a coat weight of from 0.01 to 10 g/m² on asolid basis.
 12. A surface modification process according to claim 10,wherein upon drying and curing, said coated aqueous composition isheat-treated at a temperature of at least 100° C. for at least 1 second.13. A surface modification process according to claim 10, wherein saidarticle is formed of a material selected from the group consisting ofmetals, fibers, cloths, paper, wood, plastics, synthetic resins, glass,and ceramics.
 14. A surface modification process according to claim 10,wherein said article is formed of a metal selected from the groupconsisting of iron, copper, magnesium, zinc, aluminum, and alloysthereof.
 15. A surface modification process according to claim 14,wherein the aqueous composition is directly coated onto a surface ofsaid at least one metal, and is then dried and cured.
 16. A surfacemodification process according to claim 15, wherein said article is afin blank for an air conditioner.
 17. An article comprising, on asurface thereof, a surface modifier coating formed by drying and curingan aqueous composition as defined in claim
 1. 18. An article accordingto claim 17, which is a fin blank for an air conditioner.
 19. A moldedor otherwise formed product obtained by drying and curing an aqueouscomposition as defined in claim 1.